Allocation of Communication Resources for Control Signals in the Uplink

ABSTRACT

The disclosure relates operation where information of at least one selected resource from a pool of resources for control signals in uplink is signalled in downlink. At least one resource is selected from a pool of resources for control signals in the uplink, where after information of the selected at least one resource is signalled in the downlink. Communication of control signals in the uplink by at least one device is facilitated such that at least one non-selected resource from the pool of resources is used in sending of control signals in the uplink. The at least one resource is implicitly derived in accordance with a predefined rule.

This disclosure relates to allocation of resources for wirelesscommunications and more particularly but not explicitly to allocation ofresources for uplink control signals in a communication system.

A communication system can be seen as a facility that enablescommunication sessions between two or more nodes such as fixed or mobiledevices, machine-type terminals, access nodes such as base stations,servers and so on. A communication system and compatible communicatingentities typically operate in accordance with a given standard orspecification which sets out what the various entities associated withthe system are permitted to do and how that should be achieved. Forexample, the standards, specifications and related protocols can definethe manner how devices shall communicate, how various aspects ofcommunications shall be implemented and how devices for use in thesystem shall be configured.

A user can access the communication system by means of an appropriatecommunication device. A communication device of a user is often referredto as user equipment (UE) or terminal. A communication device isprovided with an appropriate signal receiving and transmittingarrangement for enabling communications with other parties. Typically adevice such as a user equipment is used for enabling receiving andtransmission of communications such as speech and content data.

Communications can be carried on wireless carriers. Examples of wirelesssystems include public land mobile networks (PLMN) such as cellularnetworks, satellite based communication systems and different wirelesslocal networks, for example wireless local area networks (WLAN). Inwireless systems a communication device provides a transceiver stationthat can communicate with another communication device such as e.g. abase station of an access network and/or another user equipment. The twodirections of communications between a base station and communicationdevices of users have been conventionally referred to as downlink anduplink. Downlink (DL) can be understood as the direction from the basestation to the communication device and uplink (UL) the direction fromthe communication device to the base station.

In certain systems allocation of resources for the downlink and theuplink are handled independently. Uplink (UL) assignments or grants sentto the user equipment (UE) are used to inform the user equipment ofresources the UE shall use to transmit data. By means of the grantsdynamic allocation of resources can be provided. Transmission of thescheduling information causes scheduling overhead.

Signalling of other types of control information is also needed. Thecontrol information may be communicated for example on physical uplinkcontrol channel (PUCCH). For example, signalling for the purposes oferror detection and/or correction may be provided by means of suchsignalling. Requests for retransmission of any information that therecipient node did not successfully receive are possible. For example,hybrid automatic repeat request (HARQ) error control mechanism may beused for this purpose. The error control mechanism can be implementedsuch that a transmitting device shall receive either a positive or anegative acknowledgement (ACK/NACK; A/N) or other indication regardingits transmission from a receiving device.

An example of resource allocation for HARQ can be given in the contextof a concept known as carrier aggregation (CA). In carrier aggregationmore than one carrier can be used for communications between twodevices. In CA, when physical control channel (PDCCH) is from a servingcell, a pool of N HARQ-ACK resources are defined for user equipment (UE)and one of these resources is selected by a controlling network elementto carry ACK/NACK payload. Information of all N resources in the pool isexplicitly signalled via radio resource control (RRC) to the userequipment.

Increased utilization of advanced systems for various scenarios anddifferent data traffic types increases the need to optimize the systemfurther for a large number of users. A way to achieve this is to improvescheduling efficiency. In particular, reduction in scheduling overheadmay be desired. It might be desired in certain applications to reducedownlink control signalling overhead caused by uplink and downlinkscheduling. Optimization of signalling on physical downlink controlchannel (PDCCH) could be of particular advantage.

It is noted that the above discussed issues are not limited to anyparticular communication environment and station apparatus, but mayoccur in any appropriate station apparatus where internal communicationsare required.

Embodiments of the invention aim to address one or several of the aboveissues.

In accordance with an embodiment there is provided an apparatus for anetwork element, the apparatus comprising at least one processor, and atleast one memory including computer program code, wherein the at leastone memory and the computer program code are configured, with the atleast one processor, to select at least one resource from a pool ofresources for control signals in the uplink, cause signalling ofinformation of the selected at least one resource in the downlink, andfacilitate communication of control signals in the uplink by at leastone device based on at least one non-selected resource from the pool ofresources, wherein the at least one resource is implicitly derived inaccordance with a predefined rule.

According to another aspect, there is provided an apparatus for acommunication device for enabling operation thereof in a system whereinformation of at least one selected resource from a pool of resourcesfor control signals in the uplink is signalled in the downlink, theapparatus comprising at least one processor, and at least one memoryincluding computer program code, wherein the at least one memory and thecomputer program code are configured, with the at least one processor,to implicitly derive at least one non-selected resource from the pool ofresources for control signals in the uplink in accordance with apredefined rule, and cause sending of control signals in the uplink onthe derived at least one non-selected resource.

According to another aspect, there is provided a method for controllingcommunications, comprising selecting at least one resource from a poolof resources for control signals in the uplink, signalling informationof the selected at least one resource in the downlink, and facilitatingcommunication of control signals in the uplink by at least one devicebased on at least one non-selected resource from the pool of resources,wherein the at least one resource is implicitly derived in accordancewith a predefined rule.

According to yet another aspect, there is provided a method for enablingoperation of a communication device in a communication system whereinformation of at least one resource selected from a pool of resourcesfor control signals in the uplink is signalled in the downlink, themethod comprising implicitly deriving at least one non-selected resourcefrom the pool of resources for control signals in the uplink inaccordance with a predefined rule, and sending of control signals in theuplink on the derived at least one non-selected resource.

According to a more detailed aspect, signalling of error correctionfunction messages in a physical uplink control channel is enabled bymeans of the at least one non-selected resource.

Messages may be signalled in a physical uplink control channel by meansof the at least one non-selected resource, the resource being determinedbased on an enhanced physical downlink control channel.

At least first and second devices may communicate in the uplink. Thefirst devices may be configured for a physical downlink control channeland to signal control signals in the selected resources and the seconddevices may be configured for an enhanced physical downlink controlchannel and to signal control signals in the non-selected resources.Different uplink resources may be allocated for the first and seconddevices based on an offset parameter.

At least some information for deriving the non-selected resources may bederived based on information of the selected resources.

In accordance with a detailed embodiment a pool of resources may bedefined for uplink hybrid automatic repeat request messages, eachresource having an index. At least one of the resources may be selecteddynamically and information about the index or indexes of thedynamically selected resource may be conveyed on an enhanced physicaldownlink control channel. The at least one non-selected resource canthen be derived based on the index information and an offset. Said indexinformation may be signalled by means of a transmit power controlmessage.

At least one non-selected resource may be derived implicitly based on atleast one parameter associated with an enhanced physical downlinkcontrol channel, physical downlink shared channel and/or a communicationdevice.

A common implicit rule may be used for all channels. A dynamic modifiermay be used for distinguishing different uses.

A node such as a base station or a communication device of a user ofmachine type terminal can be configured to operate in accordance withthe various embodiments.

A computer program comprising program code means adapted to perform themethod may also be provided. The computer program may be stored and/orotherwise embodied by means of a carrier medium.

It should be appreciated that any feature of any aspect may be combinedwith any other feature of any other aspect.

Embodiments will now be described in further detail, by way of exampleonly, with reference to the following examples and accompanyingdrawings, in which:

FIG. 1 shows a schematic diagram of a communication system comprisingbase station and a plurality of communication devices;

FIG. 2 shows a schematic diagram of a mobile communication deviceaccording to some embodiments;

FIG. 3 shows a schematic diagram of a control apparatus according tosome embodiments;

FIG. 4 shows a flowchart according to an embodiment;

FIG. 5 shows a PUCCH structure in accordance with an embodiment; and

FIG. 6 shows use of resources with different parameters.

In the following certain exemplifying embodiments are explained withreference to a wireless or mobile communication system serving mobilecommunication devices. Before explaining in detail the exemplifyingembodiments, certain general principles of a wireless communicationsystem, access systems thereof, and mobile communication devices arebriefly explained with reference to FIGS. 1 to 3 to assist inunderstanding the technology underlying the described examples.

An example of wireless communication systems are architecturesstandardized by the 3rd Generation Partnership Project (3GPP). A latest3GPP based development is often referred to as the long-term evolution(LTE) of the Universal Mobile Telecommunications System (UMTS)radio-access technology. The various development stages of the 3GPP LTEspecifications are referred to as releases. More recent developments ofthe LTE are often referred to as LTE Advanced (LTE-A). The LTE employs amobile architecture known as the Evolved Universal Terrestrial RadioAccess Network (E-UTRAN). Base stations of such systems are known asevolved or enhanced Node Bs (eNBs) and may provide E-UTRAN features suchas user plane Radio Link Control/Medium Access Control/Physical layerprotocol (RLC/MAC/PHY) and control plane Radio Resource Control (RRC)protocol terminations towards the communication devices. Other examplesof radio access system include those provided by base stations ofsystems that are based on technologies such as wireless local areanetwork (WLAN) and/or WiMax (Worldwide Interoperability for MicrowaveAccess).

A device capable of wireless communications can communicate via at leastone base station or similar wireless transmitter and/or receiver node.In FIG. 1 a base station 10 is shown to be serving various mobiledevices 20 and a machine-like terminal 22. Base stations are typicallycontrolled by at least one appropriate controller apparatus so as toenable operation thereof and management of mobile communication devicesin communication with the base stations. The base station can beconnected further to a broader communications system 12. It shall beunderstood that a number of neighbouring and/or overlapping accesssystems or radio service areas provided by a number of base stations mayexist. A base station site can provide one or more cells or sectors,each sector providing a cell or a subarea of a cell. Each device andbase station may have one or more radio channels open at the same timeand may send signals to and/or receive signals from one or more sources.As a plurality of devices can use the same wireless resource,transmissions thereof need to be scheduled to avoid collisions and/orinterference.

A possible mobile communication device for transmitting in uplink andreceiving in downlink will now be described in more detail withreference to FIG. 2 showing a schematic, partially sectioned view of acommunication device 20. Such a communication device is often referredto as user equipment (UE) or terminal. An appropriate communicationdevice may be provided by any device capable of sending radio signals toand/or receiving radio signals. Non-limiting examples include a mobilestation (MS) such as a mobile phone or what is known as a ‘smart phone’,a portable computer provided with a wireless interface card or otherwireless interface facility, personal data assistant (PDA) provided withwireless communication capabilities, or any combinations of these or thelike. A mobile communication device may provide, for example,communication of data for carrying communications such as voice,electronic mail (email), text message, multimedia and so on. Users maythus be offered and provided numerous services via their communicationdevices. Non-limiting examples of these services include two-way ormulti-way calls, data communication or multimedia services or simply anaccess to a data communications network system, such as the Internet.Non-limiting examples of content data include downloads, television andradio programs, videos, advertisements, various alerts and otherinformation.

The device 20 is configured to receive signals in the downlink 29 overan air interface via appropriate apparatus for receiving and to transmitsignals in the uplink 28 via appropriate apparatus for transmittingradio signals. In FIG. 2 the transceiver apparatus is designatedschematically by block 26. The transceiver apparatus 26 may be providedfor example by means of a radio part and associated antenna arrangement.The antenna arrangement may be arranged internally or externally to themobile device.

A mobile communication device is also provided with at least one dataprocessing entity 21, at least one memory 22 and other possiblecomponents 23 for use in software and hardware aided execution of tasksit is designed to perform, including control of access to andcommunications with base stations and/or other communication devices.The data processing, storage and other relevant apparatus can beprovided on an appropriate circuit board and/or in chipsets. Thisapparatus is denoted by reference 24.

The user may control the operation of the mobile device by means of asuitable user interface such as key pad 25, voice commands, touchsensitive screen or pad, combinations thereof or the like. A display 27,a speaker and a microphone can be also provided. Furthermore, acommunication device may comprise appropriate connectors (either wiredor wireless) to other devices and/or for connecting externalaccessories, for example hands-free equipment, thereto.

FIG. 3 shows an example of a control apparatus 30 for a communicationsystem, for example to be coupled to and/or for controlling a basestation. In some embodiments a base station may comprise an integratedcontrol apparatus and some other embodiments the control apparatus canbe provided by separate network element. The control apparatus can beinterconnected with other control entities. The control apparatus andfunctions may be distributed between a plurality of control units. Insome embodiments each base station can comprise a control apparatus. Inalternative embodiments, two or more base stations may share a controlapparatus. The arrangement of the control depends on the standard, andfor example in accordance with the current LTE specifications noseparate radio network controller is provided. Regardless the location,the control apparatus 30 can be understood as providing control oncommunications in the service area of at least one base station. Thecontrol apparatus 30 can be configured to provide control functions inassociation with scheduling of uplink in accordance with embodimentsdescribed below. For this purpose the control apparatus can comprise atleast one memory 31, at least one data processing unit 32, 33 and aninput/output interface 34. Via the interface the control apparatus canbe coupled to a base station to cause operation of the base station inaccordance with the below described embodiments. The control apparatuscan be configured to execute an appropriate software code to provide thecontrol functions.

A wireless communication device, such as a mobile device, machine-liketerminal or a base station, can be provided with a MultipleInput/Multiple Output (MIMO) antenna system. MIMO arrangements as suchare known. MIMO systems use multiple antennas at the transmitter andreceiver along with advanced digital signal processing to improve linkquality and capacity. For example, the transceiver apparatus 26 of FIG.2 can provide a plurality of antenna ports. More data can be receivedand/or sent where there are more antennae elements.

Certain embodiments will now be described in more detail. In the methodillustrated by the flowchart of FIG. 4 a network element selects at 40at least one resource from a pool of resources for control signals inthe uplink. This resource selection can be provided dynamically.Information of the selected at least one resource is signalled at 42 inthe downlink. At 44 the network element can facilitate communication ofcontrol signals in the uplink by at least one device based on at leastone non-selected resource in the pool of resources. The non-selectedresource is implicitly derived based on a predefined rule.

According to a possibility the information of the resources can besignalled to a plurality of devices comprising at least two differentdevices, or devices operating in different modes. First devices can beenabled to operate based on a control channel such as a physicaldownlink control channel (PDCCH) and second devices can be enabledoperate based on another or additional control channel, such as anenhanced physical downlink control channel (ePDCCH). Devices in thePDCCH mode can be referred as devices in “legacy mode”. Switchingbetween the modes may be provided. For example, some devices can useePDCCH and/or PDCCH depending on the transmission mode.

Signalling of the information may be carried out separately to differentdevices. A device may not be aware of resources selected for otherdevices.

At step 46 a communication device receiving the information canimplicitly derive at least one non-selected resource for control signalsin the uplink in accordance with the predefined rule. The device canthen use this non-selected resource for sending of control signals at 48in the uplink. In the case of the two groups mentioned above, thedevices of the second group could be configured to use the non-selectedresources.

In the following certain more detailed examples in relation to use ofphysical uplink control channel (PUCCH) resources are described. Inaccordance with an embodiment evolved physical downlink control channel(ePDCCH) is used for scheduling a physical downlink shared channel(PDSCH). ePDCCH is a recent development of the LTE and is designed toimprove control channel performance. ePDCCH may be in particular usefulin connection with arrangements such as coordinated multipoint (CoMP),DL MIMO, heterogeneous networks (HetNet) and carrier aggregation,including use of extension carriers. For example, ePDCCH may be used toprovide support for increased control channel capacity, support forfrequency-domain interference control and interference coordination(ICIC), improved spatial reuse of control channel resources, support forbeamforming and/or diversity, support for operation on new carrier typesand in Multicast Broadcast Single Frequency Network (MBSFN) subframes,capability to coexist on the same carrier as legacy user equipment,ability to be scheduled frequency-selectively, ability to mitigateinter-cell interference and so on.

In accordance with an embodiment resource allocation can be providedsuch that implicit and explicit resource allocation are combined withcertain rules how to derive the non-explicitly allocated resources. Apart or even all of a pool of N resources are not explicitly selectedand conveyed by means of a DL control channel but are implicitly derivedfor communication of control signals in the uplink. For example,allocation of a PUCCH resource can be derived where ePDCCH is used forscheduling based on combination of implicit allocation (e.g. rulerelated to an ePDCCH resource and/or PDSCH resource subject to ePDCCHscheduling) and explicit allocation (e.g. certain control bits in theePDCCH). The implicit allocation can thus be derived based on apredefined set of rules related to the ePDCCH and the content thereof.The implicit part can be supported by explicit part in differentmanners, as will be explained below in the context of the more detailedembodiments.

In view of the term “pool” as used herein it is noted there can be manymore than N resources in a resource pool that are available but only oneout of N of them may be available to be selected dynamically. Forexample, a eNodeB can “preselect/configure” semi-statically N (thenumber of resources that can be dynamically indicated via ePDCCH) of theresources in the pool of available M resources and then dynamicallyselect one of the pool of N preselected resources. The number M ofresources in the pool of resources is typically considerably larger thanN. For example, N can be e.g. 4 while the total number of ACK/NACKresource in the pool can be around 100 or more.

The pool of resources may consist of PUCCH Format 1/1a/1b resources orother available in current cell. The resource pool may consist ofdynamic and semi-static parts. Dynamic part may be reserved for controlsignalling, e.g. HARQ-ACK signalling that relates to PDSCH and isscheduled via PDSCH. Semi-static part may be reserved for schedulingrequest and HARQ-ACK corresponding to semi-persistently scheduled PDSCH.

Only a part of resources in a resource pool can be selected for use incertain subframe, these resources being called herein as selectedresources. Examples of this usage include uplink HARQ-ACK signallingrelated to PDSCH and scheduled via PDCCH. This usage may also includeHARQ-ACK resources that relate to semi-persistently scheduled PDSCH andother existing use cases, including scheduling requests using PUCCHFormat 1.

Another part of the resource pool is not used by legacy mode devices.These resources can be referred to as non-selected resources. The unusedpart of the resource pool can be utilised such that at least some ofnon-selected resource can be used for uplink signalling. This usageincludes uplink control signaling related to PDSCH and scheduled viaePDCCH, as will be explained in more detail below.

The following example is given with reference to error correctionmechanism based on ACK/NACK messages. When ePDCCH is used to scheduledownlink data on physical downlink shared channel (PDSCH) one or moreuplink control channel resources for HARQ-ACK transmitted on thephysical uplink control channel (PUCCH) are needed by communicationdevices in order to be able to respond to the received PDSCH. There canbe various aspects that need to be taken into account when designingrelevant uplink control channel for an ePDCCH. For example, backwardscompatibility with devices scheduled with PDCCH can be of importance. Itis anticipated that HARQ-ACK corresponding to PDSCH scheduled via ePDCCHis able to utilize at least partly existing PUCCH format 1a/1b resourcescurrently used for PDSCH ACK/NACKs for devices in a legacy mode (e.g.current LTE capable user equipment scheduled with PDCCH). Schedulingrestrictions for devices in a legacy mode due to potential collision ofHARQ-ACK resources should be avoided whilst PUCCH overhead should bekept in its minimum. ePDCCH can provide capacity enhancement solutionfor dynamic resource allocation, an advantage that is believed to resulta greater number of devices being configured to support ePDCCH. Thenumbers can be considerable and thus an aim is to optimise use ofexisting PUCCH overhead. ePDCCH overhead may also need to be optimiseddue to HARQ-ACK resource allocation included in downlink controlinformation (DCI) formats carried via ePDCCH. Certain embodiments alsoaim to ease scheduling restrictions due to simultaneous scheduleddevices utilizing either PDCCH or ePDCCH.

In accordance with an embodiment N HARQ-ACK resources are defined. Thiscan be provided by a network element such as an eNB. The eNB can thenselect any of the N HARQ-ACK resources in current subframe for theHARQ-ACK signalling scheduled via ePDCCH. Thus some of the resources maybe “selected resources”. Information about the selection is communicatedvia explicit or implicit signalling in downlink control information(DCI). At least part of the N HARQ-ACK resources are “non-selected”,i.e., available for ePDCCH enabled devices such that at least one out ofN HARQ-ACK resources is derived implicitly in accordance with apredefined rule.

According to an embodiment at least one out of N resources can beselected dynamically based on pre-defined bits/codepoints conveyed viaePDCCH. An example of this is the 2-bit uplink transmit power controlfield. Bits specific for this purpose may also be introduced. An indexof the selected resource can be signalled via ePDCCH and can be denotedas n (n {1,2, . . . N}. At least one out of N HARQ-ACK resources canthen be derived implicitly based on the index and a predefined rulerelated to the ePDCCH, PDSCH and/or a user equipment and/or cellspecific parameter or parameters.

In accordance with an embodiment, only one HARQ-ACK resource is derivedimplicitly based on information from the network. Other (N−1) resourcescan then be derived from information regarding the implicitly derivedchannel according to a predetermined rule. For example, the otherresources can be derived based on a fixed/predefined offset from theimplicitly derived resource. An example of this is where a commonimplicit rule for all (N) HARQ-ACK resources is used. Dynamic allocationcan be used here as a modifier on top of the implicit resourceallocation, e.g. as a fixed/predefined offset with regard to theimplicit resource. The predefined modifier can be used to modify aresult given by the implicit rule in differential manner. Thus a finalresult is given by the implicit rule+a delta derived from ePDCCH. Thedelta can be e.g., [0, +1, −1, +2].

In another embodiment, k out of N (k>0) HARQ-ACK resources are derivedimplicitly whereas the other (N-k) resources are configured explicitlyby means of RRC signalling. The k implicit resources may have eithercommon or separate implicit rule.

In yet another embodiment all (N) HARQ-ACK resources are derivedimplicitly according to separate resource allocation rules. Thisapproach is based on the assumption that statistically at least one outof N resources can be considered as being free from collision.Pseudo-random rules are provided such that N different resourceopportunities are randomly (or evenly) distributed over the allowedresource space.

Various combinations of the above schemes are also possible. Forexample, some the implicit resources may have a common rule whereas someof the resources may have a rule of their own.

Thus some of the HARQ-ACK resources can be implicitly derived fromePDCCH and/or PDSCH and/or another from a resource allocated usingePDDCH. In accordance with an example, one of the N HARQ-ACK resourcesis selected and communicated via explicit signalling in downlink controlinformation (DCI). Some of the resources can be explicitly configuredvia the RRC. Some other HARQ resources may also be derived based oninformation about implicit resources. In accordance with a possibilityall resources are implicitly derived with a common rule, but with adifferent dynamic part of the signalling.

In accordance with a specific embodiment a new parameter is defined forPUCCH channelization. The parameter is denoted herein as o_(ePDCCH)^(dynamic) and may contain N separate values:

$\left( {o_{ePDCCH}^{dynamic} \in \left\lfloor \begin{matrix}O_{ePDCCH}^{1} & o_{ePDCCH}^{2} & \ldots & O_{ePDCCH}^{N}\end{matrix} \right\rfloor} \right)$

The value to be applied for resource allocation can be selecteddynamically via pre-defined log2 (N) bits or N codepoints conveyed viaePDCCH.

At least one of the entries of the parameter o_(ePDCCH) ^(dynamic) canrelate to an implicitly allocated HARQ-ACK resource. The applied PUCCHHARQ-ACK resource, n_(PUCCH) ^((1)ePDCCH), can be defined by means of anoffset with respect to known reference according to the followingequation:

n _(PUCCH) ^((1)ePDCCH) =N _(PUCCH) ⁽¹⁾ +o _(ePDCCH) ^(dynamic)(n),where

-   -   o_(ePDCCH) ^(dynamic)(n) is the offset parameter (in which at        least one value is derived implicitly based on the scheduling        ePDCCH and/or PDSCH),    -   n is the index of the dynamic part, and    -   N_(PUCCH) ⁽¹⁾ corresponds to the number of resources reserved        for persistent HARQ-ACK and scheduling request.

It is noted that an offset is may not be necessary with explicitlyconfigured (i.e. constant, independent of ePDCCH scheduling) entries of

o_(ePDCCH)^(dynamic)_

For these entries o_(ePDCCH) ^(dynamic)(n′) can relate directly to aRRC-configured resource.

It is also possible to have a fixed offset between dynamic A/N resourcesof UEs in a legacy mode (i.e when PDCCH is used) and dynamic resourcesA/N of ePDCCH UEs as shown in FIG. 5. This can be realized by means ofadditional semi-static parameter, o_(ePDCCH) ^(semi-static). Thisparameter can be either cell-specific or UE-specific. The appliedHARQ-ACK resource can be defined in this case according to the followingequation:

n _(PUCCH) ^((1)ePDCCH) =N _(PUCCH) ⁽¹⁾ +o _(ePDCCH) ^(dynamic)(n)+o_(ePDDCH) ^(semi-static).

A benefit of this approach is that it allows to trade-off the schedulerflexibility and PUCCH overhead.

Limitation in the total of control signal resources for ePDCCH may beprovided, this enabling a trade-off between PUCCH overhead and schedulerflexibility. In one embodiment an eNB can adjust the range of values forthe parameter O_(ePDCCH) ^(dynamic) in order to further trade-off thePUCCH overhead and scheduler flexibility. The maximum (and/or minimum)value of o_(ePDCCH) ^(dynamic) can be limited into a predefined valueo_(ePDCCH) ^(MAX). This can be realized e.g. by means of modulooperation mod (o_(ePDCCH) ^(dynamic), o_(ePDCCH) ^(MA). The range can beconfigured e.g., by means of RRC. It is also possible to derive therange according to the instantaneous/maximum applied physical controlformat indicator channel (PCFICH) value.

FIG. 5 shows an example of current PUCCH structure emphasizing theFormat 1a/1b resources reserved for dynamic HARQ-ACK. This figureassumes the following parameterization for HARQ-ACK resourcescorresponding to PDSCH scheduled via ePDCCH:

-   -   o_(ePDCCH) ^(semi-static)=10    -   o_(ePDCCH) ^(MAX)=29    -   mod (o_(ePDCCH) ^(dynamic, o) _(ePDCCH) ^(MAX))∈{3,9,16,22}

The amount of resources that are implicitly and explicitly allocated canbe variable. The variation can be provided within limits where at leastone out of a given number of resources can be allocated explicitly andat least one resource can be allocated implicitly.

Use of implicit resource allocation and dynamic or explicit resourceallocation for HARQ-ACK messages corresponding to PDSCH scheduled viaePDCCH can provide efficient resource utilization with existing dynamicA/N space. Also, HARQ-ACK space can be made scalable. Utilization of thesame resource pool for PUCCH HARQ ACK/NACKs (A/N) for devices in alegacy mode and ePDCCH capable devices may be enabled. This is sobecause dynamic A/N space can be better utilized while at the same timethe HARQ-ACK space can be scalable. Otherwise a separate pool would beneeded in order not to collide A/Ns of devise in a legacy mode andePDCCH capable devices.

At least some of the uplink resources can be scheduled based on implicitinformation because the explicit dynamic allocation is not likely toallocate the entire available uplink resource. This is illustrated byFIG. 6 showing a table giving the number of control channel element(CCE) resources with different bandwidth options (1.4-20 MHz) anddifferent control channel values allocated for PDCCH. More particularly,the table shows the number of CCE resources used for Physical ControlFormat Indicator Channel (PCFICH) values 1 to 4. LTE Release 8 providesone-to-one mapping between the CCE and HARQ-ACK resources reserved fordynamically scheduled PDSCH, and hence, the number of CCEs shown in FIG.6 also represents the number of HARQ-ACK resources. It can be noted thatHARQ-ACK resulting from a dynamically scheduled PDSCH can representsignificant overhead in UL side keeping in mind that in a typicalconfiguration, one physical resource block (PRB) corresponds to 18HARQ-ACK resources. Furthermore, in capacity limited case the PCFICHvalue is likely to be 3, thus reserving a considerable amount ofresources. On the other hand, the inventors have recognised that inpractice only a fraction of the dynamic HARQ-ACK resources are actuallyused. This can be so because a part of the CCEs are reserved for DCIformat 0/3/3A/4, these being uplink (0 and 4) and power control grants(3/3A) which do not even trigger HARQ-ACK in the uplink. Furthermore, ina typical case PDCCH for a given user equipment consists of more thanone control channel element (CCE) resource to facilitate linkadaptation, the average number in macro environment being about 2.5CCEs/PDCCH. An outcome of this is that less than ⅓ of the resourcesreserved for dynamic HARQ-ACK may actually be used on average. Thereforea reasonable amount of unused resources are believed to be available forthe implicit allocation as discussed above.

The embodiments may save PUCCH resources and this way more PRBs may beused for PUSCH. Thus control channel overhead may be decreased.Combination of explicit and implicit allocation of resources may be usedto allow a better utilization of existing error correction messagingspace and/or for a better scalability in general.

The above described principles may also be used in connection withcarrier aggregation and/or time division duplexing (TDD). In thesecases, multiple HARQ-ACKs can be signalled e.g. by using PUCCH format 1bwith channel selection. For the HARQ-ACK signalling, multiple PUCCHresources from the N resources can be selected dynamically. Also in thiscase, amount of implicitly and explicitly allocated resources may vary.

It is noted that whilst embodiments have been described in relation toLTE, similar principles can be applied to any other communication systemor to further developments with LTE. Also, instead of scheduling that isprovided by a control apparatus associated with a base stationscheduling may be provided by any apparatus for scheduling transmissionsin two directions between at least two devices. Thus, although theembodiments are described with references to uplink and downlink, thisdisclosure is not limited by these directions between a base station anda user terminal. Instead, the invention is applicable any system where acontrol apparatus can schedule transmissions between two or morecommunicating entities, wherein the scheduling entity can be seen asbeing in the “upper” end of the link. For example, this may be the casein application where no fixed equipment provided but a communicationsystem is provided by means of a plurality of user equipment, forexample in adhoc networks. Therefore, although certain embodiments weredescribed above by way of example with reference to certain exemplifyingarchitectures for wireless networks, technologies and standards,embodiments may be applied to any other suitable forms of communicationsystems than those illustrated and described herein.

The required data processing apparatus and functions of a base stationapparatus, a communication device and any other appropriate apparatusmay be provided by means of one or more data processors. The describedfunctions at each end may be provided by separate processors or by anintegrated processor. The data processors may be of any type suitable tothe local technical environment, and may include one or more of generalpurpose computers, special purpose computers, microprocessors, digitalsignal processors (DSPs), application specific integrated circuits(ASIC), gate level circuits and processors based on multi core processorarchitecture, as non limiting examples. The data processing may bedistributed across several data processing modules. A data processor maybe provided by means of, for example, at least one chip. Appropriatememory capacity can also be provided in the relevant devices. The memoryor memories may be of any type suitable to the local technicalenvironment and may be implemented using any suitable data storagetechnology, such as semiconductor based memory devices, magnetic memorydevices and systems, optical memory devices and systems, fixed memoryand removable memory.

In general, the various embodiments may be implemented in hardware orspecial purpose circuits, software, logic or any combination thereof.Some aspects of the invention may be implemented in hardware, whileother aspects may be implemented in firmware or software which may beexecuted by a controller, microprocessor or other computing device,although the invention is not limited thereto. While various aspects ofthe invention may be illustrated and described as block diagrams, flowcharts, or using some other pictorial representation, it is wellunderstood that these blocks, apparatus, systems, techniques or methodsdescribed herein may be implemented in, as non-limiting examples,hardware, software, firmware, special purpose circuits or logic, generalpurpose hardware or controller or other computing devices, or somecombination thereof. The software may be stored on such physical mediaas memory chips, or memory blocks implemented within the processor,magnetic media such as hard disk or floppy disks, and optical media suchas for example DVD and the data variants thereof, CD.

The foregoing description has provided by way of exemplary andnon-limiting examples a full and informative description of theexemplary embodiment of this invention. However, various modificationsand adaptations may become apparent to those skilled in the relevantarts in view of the foregoing description, when read in conjunction withthe accompanying drawings and the appended claims. However, all such andsimilar modifications of the teachings of this invention will still fallwithin the scope of this invention as defined in the appended claims.Indeed there is a further embodiment comprising a combination of one ormore of any of the other embodiments previously discussed.

1. An apparatus comprising at least one processor, and at least onememory including computer program code, wherein the at least one memoryand the computer program code are configured, with the at least oneprocessor, to perform or control at least the following: select at leastone resource from a pool of resources for control signals in the anuplink; cause signaling of information of the selected at least oneresource in the a downlink; and facilitate communication of controlsignals in the uplink by at least one device based on at least onenon-selected resource from the pool of resources, wherein the at leastone resource is implicitly derived in accordance with a predefined rule.2. An apparatus comprising at least one, processor, and at least onememory including computer program code, wherein the at least one memoryand the computer program code are configured, with the at least oneprocessor, to perform or control at least the following: implicitlyderive, in a communication system where information of at least oneselected resource from a pool of resources for control signals in anuplink has been signaled in a downlink, at least one non-selectedresource from the pool of resources for control signals in the uplink inaccordance with a predefined rule; and cause sending of control signalsin the uplink on the derived at least one non-selected resource.
 3. Theapparatus of claim 1, wherein the at least one memory and the computerprogram code are further configured, with the at least one processor, toperform or control at least the following: enable signaling of errorcorrection function messages in a physical uplink control channel bymeans of the at least one non-selected resource.
 4. The apparatus ofclaim 1, wherein the at least one memory and the computer program codeare further configured, with the at least one processor, to perform orcontrol at least the following: enable signaling of messages in aphysical uplink control channel by means of the at least onenon-selected resource determined based on an enhanced physical downlinkcontrol channel.
 5. The apparatus of claim 1, wherein at least first andsecond devices communicate in the uplink, the first devices beingconfigured for a physical downlink control channel and to signal controlsignals in the selected resources and the second devices beingconfigured for an enhanced physical downlink control channel and tosignal control signals in the non-selected resources.
 6. The apparatusof claim 5, wherein the at least one memory and the computer programcode are further configured, with the at least one processor, to performor control at least the following: allocate different uplink resourcesfor the first and second devices based on an offset parameter.
 7. Theapparatus of claim 1, wherein at least some information needed to derivethe non-selected resources is derived based on information of theselected resources.
 8. The apparatus of claim 1, wherein the at leastone memory and the computer program code are further configured, withthe at least one processor, to perform or control at least thefollowing: define a pool of resources for uplink hybrid automatic repeatrequest messages, each resource having an index; select dynamically atleast one of the resources; convey information about the index orindexes of the dynamically selected resource on an enhanced physicaldownlink control channel; and derive the at least one non-selectedresource based on the index information and an offset.
 9. (canceled) 10.The apparatus of claim 1, wherein at least one non-selected resource isderived implicitly based on at least one parameter associated with anenhanced physical downlink control channel, physical downlink sharedchannel and/or a communication device.
 11. A method comprising:selecting at least one resource from a pool of resources for controlsignals in the an uplink; signaling information of the selected at leastone resource in a downlink; and facilitating communication of controlsignals in the uplink by at least one device based on at least onenon-selected resource from the pool of resources, wherein the at leastone resource is implicitly derived in accordance with a predefined rule.12. A method comprising implicitly deriving, by a communication devicein a communication system where information of at least one resourceselected from a pool of resources for control signals in an uplink hasbeen signaled in a downlink, at least one non-selected resource from thepool of resources for control signals in the uplink in accordance with apredefined rule; and sending of control signals in the uplink on thederived at least one non-selected resource.
 13. The method of claim 11,further comprising: signaling of automatic repeat request messages in aphysical uplink control channel on the at least one non-selectedresource.
 14. The method of claim 11, further comprising: deriving theat least one non-selected resource based on an enhanced physicaldownlink control channel.
 15. The method of claim 11, wherein the poolof resources comprises resources reserved for dynamic hybrid automaticrepeat request messages in the uplink responsive to data in a sharedchannel in the downlink.
 16. The method of claim 11, wherein the devicescomprise: first devices and second devices, the first devices beingconfigured for a physical downlink control channel and communicateuplink control signals in the selected resources and the second devicesbeing configured for an enhanced physical downlink control channel andcommunicate uplink control signals in the non-selected resources. 17.The method of claim 16, further comprising: separating the uplinkresources for the first and second devices based on an offset parameter.18. The method of claim 11, further comprising: using a common implicitrule for all channels and a dynamic modifier.
 19. (canceled) 20.(canceled)
 21. (canceled)
 22. (canceled)
 23. A computer program productembodied on a non-transitory computer-readable medium in which acomputer program is stored that, when being executed by a computer, isconfigured to provide instructions to control or perform the method ofclaim
 11. 24. A computer program product embodied on a non-transitorycomputer-readable medium in which a computer program is stored that,when being executed by a computer, is configured to provide instructionsto control or perform the method of claim 12.